This is quite simple
Download generic 534 (I used for central Europe)
Flash it via Flashtool and root with Kingo or root this way :
This method works great. If you don't trust these tools(Kingo root), use Root MANY ANDROID from Bin4ry. I've used this tool without any problems on the downgraded firmware.
Then boot ROM (you will need to restart your device two times to root proper) and you'll get OTA warning you have 257 firmware ready for update.
Download update and let the device flash the update.
And that's it
Now you have newest firmware and you root is here as well...
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